Semiconductor light emitting device, method of manufacturing the same, and semiconductor light emitting device package using the same

ABSTRACT

There is provided a semiconductor light emitting device, a method of manufacturing the same, and a semiconductor light emitting device package using the same. A semiconductor light emitting device having a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, a second electrode layer, and insulating layer, a first electrode layer, and a conductive substrate sequentially laminated, wherein the second electrode layer has an exposed area at the interface between the second electrode layer and the second conductivity type semiconductor layer, and the first electrode layer comprises at least one contact hole electrically connected to the first conductivity type semiconductor layer, electrically insulated from the second conductivity type semiconductor layer and the active layer, and extending from one surface of the first electrode layer to at least part of the first conductivity type semiconductor layer.

RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.12/189,428, filed on Aug. 11, 2008, claims the priority of Korean PatentApplication No. 10-2007-0105365 filed on Oct. 19, 2007, in the KoreanIntellectual Property Office, the entire contents of each of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light emitting device,a method of manufacturing the same, and a semiconductor light emittingdevice package using the same, and more particularly, to a semiconductorlight emitting device that ensures a maximum light emitting area tomaximize luminous efficiency and perform uniform current spreading byusing an electrode having a small area, and enables mass production atlow cost with high reliability and high quality, a method ofmanufacturing the same, and a semiconductor light emitting devicepackage using the same.

2. Description of the Related Art

Semiconductor light emitting devices include materials that emit light.For example, light emitting diodes (LEDs) are devices that use diodes,to which semiconductors are bonded, convert energy generated bycombination of electrons and holes into light, and emit light. Thesemiconductor light emitting devices are being widely used as lighting,display devices, and light sources, and development of semiconductorlight emitting devices has been expedited.

In particular, the widespread use of cellular phone keypads, sideviewers, and camera flashes, which use GaN-based light emitting diodesthat have been actively developed and widely used in recent years,contribute to the active development of general illumination that useslight emitting diodes. Applications of the light emitting diodes, suchas backlight units of large TVs, headlights of cars, and generalillumination, have advanced from small portable products to largeproducts having high power, high efficiency, and high reliability.Therefore, there has been a need for light sources that havecharacteristics required for the corresponding products.

In general, a semiconductor junction light emitting device has astructure in which p-type and n-type semiconductors are bonded to eachother. In the semiconductor junction structure, light may be emitted byrecombination of electrons and holes at a region where the two types ofsemiconductors are bonded to each other. In order to activate the lightemission, an active layer may be formed between the two semiconductors.The semiconductor junction light emitting device includes a horizontalstructure and a vertical structure according to the position ofelectrodes of semiconductor layers. The vertical structure includes anepi-up structure and a flip-chip structure. As described above,structural characteristics of semiconductor light emitting devices thatare required according to characteristics of individual products areseriously taken into account.

FIGS. 1A and 1B are views illustrating a horizontal light emittingdevice according to the related art. FIG. 1C is a cross-sectional viewillustrating a vertical light emitting device according to the relatedart. Hereinafter, for the convenience of explanation, in FIGS. 1A to 1C,a description will be made on the assumption that an n-typesemiconductor layer is in contact with a substrate, and a p-typesemiconductor layer is formed on an active layer.

Referring to FIG. 1A, a horizontal light emitting device having anepi-up structure will be described first. In FIG. 1A, a description willbe made on the assumption that a semiconductor layer formed at theoutermost edge is a p-type semiconductor layer. A semiconductor lightemitting device 1 includes a non-conductive substrate 13, an n-typesemiconductor layer 12, an active layer 11, and a p-type semiconductorlayer 10. An n-type electrode 15 and a p-type electrode 14 are formed onthe n-type semiconductor layer 12 and the p-type semiconductor layer 10,respectively, and are connected to an external current source (notshown) to apply a voltage to the semiconductor light emitting device 1.

When a voltage is applied to the semiconductor light emitting device 1through the electrodes 14 and 15, electrons move from the n-typesemiconductor layer 12, and holes move from the p-type semiconductorlayer 10. Light is emitted by recombination of the electrons and theholes. The semiconductor light emitting device 1 includes the activelayer 11, and light is emitted from the active layer 11. In the activelayer 11, the light emission of the semiconductor light emitting device1 is activated, and light is emitted. In order to make an electricalconnection, the n-type electrode and the p-type electrode are located onthe n-type semiconductor layer 12 and the p-type semiconductor layer 10,respectively, with the lowest contact resistances.

The position of the electrodes may change according to the substratetype. For example, when the substrate 13 is a sapphire substrate that isa non-conductive substrate, the electrode of the n-type semiconductorlayer 12 cannot be formed on the non-conductive substrate 13, but on then-type semiconductor layer 12.

Therefore, referring to FIG. 1A, when the n-type electrode 15 is formedon the n-type semiconductor 12, parts of the p-type semiconductor layer10 and the active layer 12 that are formed at the upper side areconsumed to form an ohmic contact. The formation of the electroderesults in a decrease of light emitting area of the semiconductor lightemitting device 1, and thus luminous efficiency also decreases.

In FIG. 1B, a horizontal light emitting device has a structure thatincreases luminous efficiency is illustrated. The semiconductor lightemitting device, shown in FIG. 1B, is a flip chip semiconductor lightemitting device 2. A substrate 23 is located at the top. Electrodes 24and 25 are in contact with electrode contacts 26 and 27, respectively,which are formed on a conductive substrate 28. Light emitted from anactive layer 21 is emitted through the substrate 23 regardless of theelectrodes 24 and 25. Therefore, the decrease in luminous efficiencythat is caused in the semiconductor light emitting device, shown in FIG.1A, can be prevented.

However, despite the high luminous efficiency of the flip chip lightemitting device 2, the n-type electrode and the p-type electrode in thelight emitting device 2 need to be disposed in the same plane and bondedin the semiconductor light emitting device 2. After being bonded, then-type electrode and the p-type electrode are likely to be separatedfrom the electrode contacts 26 and 27. Therefore, there is a need forexpensive precision processing equipment. This causes an increase inmanufacturing costs, a decrease in productivity, a decrease in yield,and a decrease in product reliability.

In order to solve a variety of problems including the above-describedproblems, a vertical light emitting device that uses a conductivesubstrate, not the non-conductive substrate, appeared. A light emittingdevice 3, shown in FIG. 1C, is a vertical light emitting device. When aconductive substrate 33 is used, an n-type electrode 35 may be formed onthe substrate 33. The conductive substrate 33 may be formed of aconductive material, for example, Si. In general, it is difficult toform semiconductor layers on the conductive substrate due tolattice-mismatching. Therefore, semiconductor layers are grown by usinga substrate that allows easy growth of the semiconductor layers, andthen a conductive substrate is bonded after removing the substrate forgrowth.

When the non-conductive substrate is removed, the conductive substrate33 is formed on the n-type semiconductor layer 32, such that the lightemitting device 3 has a vertical structure. When the conductivesubstrate 33 is used, since a voltage can be applied to the n-typesemiconductor layer 32 through the conductive substrate 33, an electrodecan be formed on the substrate 33. Therefore, as shown in FIG. 1C, then-type electrode 35 is formed on the conductive substrate 33, and thep-type electrode 34 is formed on the p-type semiconductor layer 30, suchthat the semiconductor light emitting device having the verticalstructure can be manufactured.

However, when a high-power light emitting device having a large area ismanufactured, an area ratio of the electrode to the substrate needs tobe high for current spreading. Therefore, light extraction is limited,light loss is caused by optical absorption, luminous efficiencydecreases, and product reliability is reduced.

SUMMARY OF THE INVENTION

An aspect of the present invention provides to a semiconductor lightemitting device that ensures a maximum light emitting area to maximizeluminous efficiency and perform uniform current spreading by using anelectrode having a small area, and enables mass production at low costwith high reliability and high quality, a method of manufacturing thesame, and a semiconductor light emitting device package using the same.

According to an aspect of the present invention, there is provided asemiconductor light emitting device having a first conductivity typesemiconductor layer, an active layer, a second conductivity typesemiconductor layer, a second electrode layer, and insulating layer, afirst electrode layer, and a conductive substrate sequentiallylaminated, wherein the second electrode layer has an exposed area at theinterface between the second electrode layer and the second conductivitytype semiconductor layer, and the first electrode layer comprises atleast one contact hole electrically connected to the first conductivitytype semiconductor layer, electrically insulated from the secondconductivity type semiconductor layer and the active layer, andextending from one surface of the first electrode layer to at least partof the first conductivity type semiconductor layer.

The semiconductor light emitting device may further include an electrodepad unit formed at the exposed area of the second electrode layer.

The exposed area of the second electrode layer may be a region exposedby a via hole formed through the first conductivity type semiconductorlayer, the active layer, and the second conductivity type semiconductorlayer.

The diameter of the via hole may increase in a direction from the secondelectrode layer toward the first conductivity type semiconductor layer.

An insulating layer may be formed on an inner surface of the via hole.

The exposed area of the second electrode layer may be formed at the edgeof the semiconductor light emitting device.

The second electrode layer may reflect light generated from the activelayer.

The second electrode layer may include one metal selected from a groupconsisting of Ag, Al, and Pt.

An irregular pattern may be formed on the surface of the firstconductivity type semiconductor layer.

The irregular pattern may have a photonic crystal structure.

The conductive substrate may include one metal selected from a groupconsisting of Au, Ni, Cu, and W.

The conductive substrate may include one selected from a groupconsisting of Si, Ge, and GaAs.

According to another aspect of the present invention, there is provideda method of manufacturing a semiconductor light emitting device, themethod including: sequentially laminating a first conductivity typesemiconductor layer, an active layer, a second conductivity typesemiconductor layer, a second electrode layer, an insulating layer, afirst electrode layer, and a conductive substrate; forming an exposedarea at the interface between the second electrode layer and the secondconductivity type semiconductor layer; and forming at least one contacthole in the first electrode layer, the contact hole electricallyconnected to the first conductivity type semiconductor layer,electrically insulated from the second conductivity type semiconductorlayer and the active layer, and extending from one surface of the firstelectrode layer to at least part of the first conductivity typesemiconductor layer.

The forming an exposed area of the second electrode layer may includemesa etching the first conductivity type semiconductor layer, the activelayer, and the second conductivity type semiconductor layer.

The conductive substrate may be formed by plating method and laminated.The conductive substrate may be laminated by a substrate bonding method.

According to still another aspect of the present invention, there isprovided a semiconductor light emitting device package including: asemiconductor light emitting device package body having a recessed partformed at an upper surface thereof; a first lead frame and a second leadframe mounted to the semiconductor light emitting device package body,exposed at a lower surface of the recessed part, and separated from eachother by a predetermined distance; a semiconductor light emitting devicemounted to the first lead frame, wherein the semiconductor lightemitting device has a first conductivity type semiconductor layer, anactive layer, a second conductivity type semiconductor layer, a secondelectrode layer, an insulating layer, a first electrode layer, and aconductive substrate sequentially laminated, the second electrode layercomprises an exposed area at the interface between the second electrodelayer and the second conductivity type semiconductor layer, and thefirst electrode layer comprises at least one contact hole electricallyconnected to the first conductivity type semiconductor layer,electrically insulated from the second conductivity type semiconductorlayer and the active layer, and extending from one surface of the firstelectrode layer to at least part of the first conductivity typesemiconductor layer.

The semiconductor light emitting device may further include an electrodepad unit formed at the exposed area of the second electrode layer, andthe electrode pad unit is electrically connected to the second leadframe.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1A is a cross-sectional view illustrating a horizontal lightemitting device.

FIG. 1B is a cross-sectional view illustrating the horizontal lightemitting device.

FIG. 1C is a cross-sectional view illustrating a vertical light emittingdevice.

FIG. 2 is a perspective view illustrating a semiconductor light emittingdevice according to an exemplary embodiment of the present invention.

FIG. 3 is a plan view illustrating the semiconductor light emittingdevice shown in FIG. 2.

FIG. 4A is a cross-sectional view illustrating the semiconductor lightemitting device, shown in FIG. 3, taken along the line A-A′.

FIG. 4B is a cross-sectional view illustrating the semiconductor lightemitting device, shown in FIG. 3, taken along the line B-B′.

FIG. 4C is a cross-sectional view illustrating the semiconductor lightemitting device, shown in FIG. 3, taken along the line C-C′.

FIG. 5 is a view illustrating light emission in the semiconductor lightemitting device having an irregular pattern at the surface thereofaccording to the embodiment of the present invention.

FIG. 6 is a view illustrating a second electrode layer exposed at theedge of the semiconductor light emitting device according to anotherembodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a semiconductor lightemitting package according to still another embodiment of the presentinvention.

FIG. 8 is a graph illustrating the relationship between luminousefficiency and current density of a light emitting surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings. The invention mayhowever be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art.

FIG. 2 is a perspective view illustrating a semiconductor light emittingdevice according to an exemplary embodiment of the invention. FIG. 3 isa plan view illustrating the semiconductor light emitting device shownin FIG. 2. Hereinafter, a description will be made with reference toFIGS. 2 and 3.

A semiconductor light emitting device 100 according to the exemplaryembodiment of the invention includes a first conductivity typesemiconductor layer 111, an active layer 112, a second conductivity typesemiconductor layer 113, a second electrode layer 120, a firstinsulating layer 130, a first electrode layer 140, and a conductivesubstrate 150 that are sequentially laminated. At this time, the secondelectrode layer 120 has an exposed area at the interface between thesecond electrode layer 120 and the second conductivity typesemiconductor layer 113. The first electrode layer 140 includes at leastone contact hole 141. The contact hole 141 is electrically connected tothe first conductivity type semiconductor layer 111, electricallyinsulated from the second conductivity type semiconductor layer 113 andthe active layer 112, and extends from one surface of the firstelectrode layer 140 to at least part of the first conductivity typesemiconductor layer 111.

In the semiconductor light emitting device 100, the first conductivitytype semiconductor layer 111, the active layer 112, and the secondconductivity type semiconductor layer 113 perform light emission.Hereinafter, they are referred to as a light emitting lamination 110.That is, the semiconductor light emitting device 100 includes the lightemitting lamination 110, the first electrode layer 140, and the firstinsulating layer 130. The first electrode layer 140 is electricallyconnected to the first conductivity type semiconductor layer 111. Thesecond electrode layer 120 is electrically connected to the secondconductivity type semiconductor layer 113. The first insulating layer130 electrically insulates the electrode layers 120 and 140 from eachother. Further, the conductive substrate 150 is included as a substrateto grow or support the semiconductor light emitting device 100.

Each of the semiconductor layers 111 and 113 may be formed of asemiconductor, such as a GaN-based semiconductor, a ZnO-basedsemiconductor, a GaAs-based semiconductor, a GaP-based semiconductor,and a GaAsP-based semiconductor. The semiconductor layer may be formedby using, for example, molecular beam epitaxy (MBE). In addition, eachof the semiconductor layers may be formed of any one of semiconductors,such as a III-V semiconductor, a II-VI semiconductor, and Si. Each ofthe semiconductor layers 111 and 113 is formed by doping theabove-described semiconductor with appropriate impurities inconsideration of the conductivity type.

The active layer 112 is a layer where light emission is activated. Theactive layer 112 is formed of a material that has a smaller energybandgap than each of the first conductivity type semiconductor layer 111and the second conductivity type semiconductor layer 113. For example,when each of the first conductivity type semiconductor layer 111 and thesecond conductivity type semiconductor layer 113 is formed of aGaN-based compound, the active layer 112 may be formed by using anInAlGaN-based compound semiconductor that has a smaller energy bandgapthan GaN. That is, the active layer 112 may includeIn_(x)Al_(y)Ga_((1-x-y))N (0≦x≦1, 0≦y≦1, 0≦x+y≦1).

In consideration of characteristics of the active layer 112, the activelayer 120 is preferably not doped with impurities. A wavelength of lightemitted can be controlled by adjusting a mole ratio of constituents.Therefore, the semiconductor light emitting device 100 can emit any oneof infrared light, visible light, and UV light according to thecharacteristics of the active layer 112.

Each of the electrode layers 120 and 140 is formed in order to apply avoltage to the same conductivity type semiconductor layer. Therefore, inconsideration of electroconductivity, the electrode layers 120 and 140may be formed of metal. That is, the electrode layers 120 and 140include electrodes that electrically connect the semiconductor layers111 and 113 to an external current source (not shown). The electrodelayers 120 and 140 may include, for example, Ti as an n-type electrode,and Pd or Au as a p-type electrode.

The first electrode layer 140 is connected to the first conductivitytype semiconductor layer 111, and the second electrode layer 120 isconnected to the second conductivity type semiconductor layer 113. Thatis, since the first and second layers 140 and 120 are connected to thedifferent conductivity type semiconductor layers from each other, thefirst and second layers 140 and 120 are electrically separated from eachother by the first insulating layer 130. Preferably, the firstinsulating layer 130 is formed of a material having lowelectroconductivity. The first insulating layer 130 may include, forexample, an oxide such as SiO₂.

Preferably, the second electrode layer 120 reflects light generated fromthe active layer 112. Since the second electrode layer 120 is locatedbelow the active layer 112, the second electrode layer 120 is located atthe other side of a direction in which the semiconductor light emittingdevice 100 emits light on the basis of the active layer 112. Lightmoving from the active layer 112 toward the second electrode layer 120is in an opposition direction to the direction in which thesemiconductor light emitting device 100 emits light. Therefore, thelight proceeding toward the second electrode layer 120 needs to bereflected to increase luminous efficiency. Therefore, when the secondelectrode layer 120 has light reflectivity, the reflected light movestoward a light emitting surface to thereby increase the luminousefficiency of the semiconductor light emitting device 100.

In order to reflect the light generated from the active layer 112,preferably, the second electrode layer 120 is formed of metal thatappears white in the visible ray region. For example, the white metalmay be any one of Ag, Al, and Pt.

The second electrode layer 120 includes an exposed area at the interfacebetween the second electrode layer 120 and the second conductivity typesemiconductor layer 113. A lower surface of the first electrode layer140 is in contact with the conductive substrate 150, and the firstelectrode layer 140 is electrically connected to the external currentsource (not shown) through the conductive substrate 150. However, thesecond electrode layer 120 requires a separate connecting region so asto be connected to the external current source (not shown). Therefore,the second electrode layer 120 includes an area that is exposed bypartially etching the light emitting lamination 110.

In FIG. 2, an example of a via hole 114 is shown. The via hole 114 isformed by etching the center of the light emitting lamination 110 toform an exposed area of the second electrode layer 120. An electrode padunit 160 may be further formed at the exposed area of the secondelectrode layer 120. The second electrode layer 120 can be electricallyconnected to the external power source (not shown) by the exposed regionthereof. At this time, the second electrode layer 120 is electricallyconnected to the external power source (not shown) by using theelectrode pad unit 160. The second electrode layer 120 can beelectrically connected to the external current source (not shown) by awire or the like. For convenient connection to the external currentsource, preferably, the diameter of the via hole increases from thesecond electrode layer toward the first conductivity type semiconductorlayer.

The via hole 114 is formed by selective etching. In general, the lightemitting lamination 110 including the semiconductors is only etched, andthe second electrode layer 120 including the metal is not etched. Thediameter of the via hole 114 can be appropriately determined by thoseskilled in the art in consideration of the light emitting area,electrical connection efficiency, and current spreading in the secondelectrode layer 120.

The first electrode layer 140 includes at least one contact hole 141.The contact hole 141 is electrically connected to the first conductivitytype semiconductor layer 111, electrically insulated from the secondconductivity type semiconductor layer 113 and the active layer 112, andextends to at least part of the first conductivity type semiconductorlayer 111. The first electrode layer 140 includes at least one contacthole 141 in order to connect the first conductivity type semiconductorlayer 111 to the external current source (not shown). The contact hole141 is formed through the second electrode layer 120 between the firstelectrode layer 140 and the second conductivity type semiconductor layer113, the second conductivity type semiconductor layer 113, and theactive layer 112, and extends to the first conductivity typesemiconductor layer 111. Further, the contact hole 141 is formed of anelectrode material.

When the contact hole 141 is only used for the electrical connection,the first electrode layer 140 may include one contact hole 141. However,in order to uniformly spread a current that is transmitted to the firstconductivity type semiconductor layer 111, the first electrode layer 140may include a plurality of contact holes 141 at predetermined positions.

The conductive substrate 150 is formed in contact with and iselectrically connected to the first electrode layer 140. The conductivesubstrate 150 may be a metallic substrate or a semiconductor substrate.When the conductive substrate 150 is formed of metal, the metal may beany one of Au, Ni, Cu, and W. Further, when the conductive substrate 150is the semiconductor substrate, the semiconductor substrate may beformed of any one of Si, Ge, and GaAs. The conductive substrate 150 maybe a growth substrate. Alternatively, the conductive substrate 150 maybe a supporting substrate. After a non-conductive substrate, such as asapphire substrate having small lattice-mismatching, is used as a growthsubstrate, and the non-conductive substrate is removed, the supportingsubstrate is bonded.

When the conductive substrate 150 is the supporting substrate, it may beformed by using a plating method or a substrate bonding method.Specifically, examples of a method of forming the conductive substrate150 in the semiconductor light emitting device 100 may include a platingmethod of forming a plating seed layer to form a substrate and asubstrate bonding method of separately preparing the conductivesubstrate 150 and bonding the conductive substrate 150 by using aconductive adhesive, such as Au, Au—Sn, and Pb—Sr.

FIG. 3 is a plan view illustrating the semiconductor light emittingdevice 100. The via hole 114 is formed in an upper surface of thesemiconductor light emitting device 100, and the electrode pad unit 160is positioned at the exposed region of the second electrode layer 120.In addition, though not shown in the upper surface of the semiconductorlight emitting device 100, in order to display the positions of thecontact holes 141, the contact holes 141 are shown as a dotted line todisplay the positions of the contact holes 141. The first insulatinglayer 130 may extend and surround the contact hole 141 so that thecontact hole 141 is electrically separated from the second electrodelayer 120, the second conductivity type semiconductor layer 113, and theactive layer 112. This will be described in more detail with referenceto FIGS. 4B and 4C.

FIG. 4A is a cross-sectional view illustrating the semiconductor lightemitting device, shown in FIG. 3, taken along the line A-A′. FIG. 4B isa cross-sectional view illustrating the semiconductor light emittingdevice, shown in FIG. 3, taken along the line B-B′. FIG. 4C is across-sectional view illustrating the semiconductor light emittingdevice, shown in FIG. 3, taken along the line C-C′. The line A-A′ istaken to show a cross section of the semiconductor light emitting device100. The line B-B′ is taken to show a cross section that includes thecontact holes 141 and the via hole 114. The line C-C′ is taken to show across section that only includes the contact holes 141. Hereinafter, thedescription will be described with reference to FIGS. 4A to 4C.

With reference to FIG. 4A, neither the contact hole 141 nor the via hole114 is shown. Since the contact hole 141 is not connected by using aseparate connecting line but electrically connected by the firstelectrode layer 140, the contact hole 141 is not shown in the crosssection in FIG. 3.

Referring to FIGS. 4B and 4C, the contact hole 141 extends from theinterface between the first electrode layer 140 and the second electrodelayer 120 to the inside of the first conductivity type semiconductorlayer 111. The contact hole 141 passes through the second conductivitytype semiconductor layer 113 and the active layer 112 and extends to thefirst conductivity type semiconductor layer 111. The contact hole 141extends at least to the interface between the active layer 112 and thefirst conductivity type semiconductor layer 111. Preferably, the contacthole 141 extends to part of the first conductivity type semiconductorlayer 111. However, the contact hole 141 is used for the electricalconnection and current spreading. Once the contact hole 141 is incontact with the first conductivity type semiconductor layer 111, thecontact hole 141 does not need to extend to the outer surface of thefirst conductivity type semiconductor layer 111.

The contact hole 141 is formed to spread the current in the firstconductivity type semiconductor layer 111. Therefore, a predeterminednumber of contact holes 141 are formed, and each of the contact holes141 has an area small enough to allow uniform current spreading in thefirst conductivity type semiconductor layer 111. A small number ofcontact holes 141 may cause deterioration in electrical characteristicsdue to difficulties in performing current spreading. A large number ofcontact holes 141 may cause difficulties in forming the contact holes141 and a reduction in light emitting area due to a decrease in area ofthe active layer. Therefore, each of the contact holes 141 is formed tohave as small area as possible and allow uniform current spreading.

The contact hole 141 extends from the second electrode layer 120 to theinside of the first conductivity type semiconductor layer 111. Since thecontact hole 141 is formed to spread the current in the firstconductivity type semiconductor layer, the contact hole 141 needs to beelectrically separated from the second conductivity type semiconductorlayer 113 and the active layer 112. Therefore, preferably, the contacthole 141 is electrically separated from the second electrode layer 120,the second conductivity type semiconductor layer 113, and the activelayer 112. Therefore, the first insulating layer 130 may extend whilesurrounding the contact hole 141. The electrical separation may beperformed by using an insulating material, such as a dielectric.

In FIG. 4B, the exposed region of the second electrode layer 120 isformed so that the second electrode layer 120 is electrically connectedto the external current source (not shown). The electrode pad unit 160may be positioned at the exposed region. At this time, a secondinsulating layer 170 may be formed on an inner surface of the via hole114 so that the light emitting lamination 110 and the electrode pad unit160 can be electrically separated from each other.

As shown in FIG. 4A, since the first electrode layer 140 and the secondelectrode layer 120 are formed in the same plane, the semiconductorlight emitting device 100 has characteristics of the horizontalsemiconductor light emitting device 100. As shown in FIG. 4B, since theelectrode pad unit 160 is formed at the surface of the secondconductivity type semiconductor layer 120, the semiconductor lightemitting device 100 can have characteristics of the vertical lightemitting device. Therefore, the semiconductor light emitting device 100has a structure into which the vertical structure and the horizontalstructure are integrated.

In FIGS. 4A to 4C, the first conductivity type semiconductor layer 111may be an n-type semiconductor layer, and the first electrode layer 140may be an n-type electrode. In this case, the second conductivity typesemiconductor layer 113 may be a p-type semiconductor layer, and thesecond electrode layer 120 may be a p-type electrode. Therefore, thefirst electrode layer 140 formed of the n-type electrode and the secondelectrode layer 120 formed of the p-type electrode may be electricallyinsulated from each other with the first insulating layer 130 interposedtherebetween.

FIG. 5 is a view illustrating light emission in a semiconductor lightemitting device having an irregular pattern formed at the surfacethereof according to an exemplary embodiment of the present invention.The description of the same components that have already been describedwill be omitted.

In the semiconductor light emitting device 100 according to theexemplary embodiment of the invention, the first conductivity typesemiconductor layer 111 forms the outermost edge in a direction in whichemitted light moves. Therefore, an irregular pattern 180 can be easilyformed on the surface by using a known method, such as photolithography.In this case, the light emitted from the active layer 112 passes throughthe irregular pattern 180 formed at the surface of the firstconductivity type semiconductor layer 111, and then the light isextracted. The irregular pattern 180 results in an increase in lightextraction efficiency.

The irregular pattern 180 may have a photonic crystal structure.Photonic crystals contain different media that have different refractiveindexes and are regularly arranged like crystals. The photonic crystalscan increase light extraction efficiency by controlling light in unit oflength corresponding to a multiple of a wavelength of light.

FIG. 6 is a view illustrating a second electrode layer exposed at theedge of a semiconductor light emitting device according to anotherexemplary embodiment of the present invention.

According to another exemplary embodiment of the present invention, amethod of manufacturing a semiconductor light emitting device isprovided. The method includes sequentially laminating a firstconductivity type semiconductor layer 211, an active layer 212, a secondconductivity type semiconductor layer 213, a second electrode layer 220,an insulating layer 230, a first electrode layer 240, and a conductivesubstrate 250; forming an exposed area at the interface between thesecond electrode layer 220 and the second conductivity typesemiconductor layer 213; and forming at least one contact hole 241 inthe second conductivity type semiconductor layer 213, the contact hole241 electrically connected to the first conductivity type semiconductorlayer 211, electrically insulated from the second conductivity typesemiconductor layer 213 and the active layer 212, and extending from onesurface of the first electrode layer 240 to at least part of the firstconductivity type semiconductor layer 211.

At this time, the exposed area of the second electrode layer 220 may beformed by forming the via hole 214 in a light emitting lamination 210(refer to FIG. 2). Alternatively, as shown in FIG. 6, the exposed areaof the second electrode layer 220 may be formed by mesa etching thelight emitting lamination 210. In this embodiment, the description ofthe same components as those of the embodiment that has been describedwith reference to 2 will be omitted.

Referring to FIG. 6, one edge of a semiconductor light emitting device200 is mesa etched. The edge of the semiconductor light emitting device200 is etched to expose the second electrode layer 220 at the interfacebetween the second electrode layer 220 and the second conductivity typesemiconductor layer 213. The exposed area of the second electrode layer220 is formed at the edge of the semiconductor light emitting device200. A process of forming the exposed region at the edge of thesemiconductor light emitting device 200 is simpler than the process offorming the via hole in the above-described embodiment, and also allowsa subsequent process of electrical connection to be easily performed.

FIG. 7 is a cross-sectional view illustrating a semiconductor lightemitting device package 300 according to still another embodiment of thepresent invention. The semiconductor light emitting device package 300includes a semiconductor light emitting device package body 360 a, 360b, and 360 c having an upper surface in which a recessed part is formed,a first lead frame 370 a and a second lead frame 370 b mounted to thesemiconductor light emitting device package body 360 a, 360 b, and 360c, exposed at a lower surface of the recessed part, and separated fromeach other by a predetermined distance, and a semiconductor lightemitting device 310 and 320 mounted to the first lead frame 370 a. Thesemiconductor light emitting device 310 and 320 is the semiconductorlight emitting device having the via hole at the center thereofaccording to the exemplary embodiment of the invention that has beendescribed with reference to FIG. 2. The description of the samecomponents having been described will be omitted.

The semiconductor light emitting device 310 and 320 includes a lightemitting unit 310 and a conductive substrate 320. The light emittingunit 310 includes first and second semiconductor layers, an activelayer, and electrode layers. A via hole is formed in the light emittingunit 310, and the semiconductor light emitting device 310 and 320further includes an electrode pad unit 330 at an exposed region. Theconductive substrate 320 is electrically connected to the first leadframe 370 a, and the electrode pad unit 330 is electrically connected tothe second lead frame 370 b by a wire 340 or the like.

The semiconductor light emitting device 310 and 320 is electricallyconnected to the second lead frame 370 b, to which the semiconductorlight emitting device 310 and 320 is not mounted, by wire bonding 340.Therefore, the semiconductor light emitting device can obtain highluminous efficiency and has a vertical structure. As shown in FIG. 7,the semiconductor light emitting device is mounted to the lead frame 370a by die bonding and to the lead frame 370 b by wire bonding. Therefore,the process can be performed at relatively low costs.

FIG. 8 is a graph illustrating the relationship between luminousefficiency and current density of a light emitting surface. When currentdensity is about 10 A/cm² or more, if the current density is low,luminous efficiency is high, and if the current density is high,luminous efficiency is low.

The relationship between the current density and the luminousefficiency, and light emitting area are numerically shown in Table 1.

TABLE 1 Current Luminous Light emitting density efficiency Improvementarea (cm²) (A/cm²) (lm/W) (%) 0.0056 62.5 46.9 100 0.0070 50.0 51.5 1100.0075 46.7 52.9 113 0.0080 43.8 54.1 115

Referring to FIG. 8 and Table 1, as the light emitting area increases,luminous efficiency increases. However, in order to ensure the lightemitting area, the area of the distributed electrodes needs to bereduced, which reduces current density of the light emitting surface.The reduction in current density of the light emitting surface maydeteriorate electrical characteristics of the semiconductor lightemitting device.

However, this problem can be solved by ensuring current spreading byusing contact holes according to the embodiments of the invention.Therefore, the deterioration in electrical characteristics that may becaused by the reduction in current density can be prevented by using amethod of forming contact holes in the semiconductor light emittingdevice that do not extend to the light emitting surface for currentspreading but are formed therein. Therefore, the semiconductor lightemitting device according to the embodiments of the invention performsdesired current spreading and ensures a maximum light emitting area toobtain desirable luminous efficiency.

As set forth above, according to exemplary embodiments of the invention,the semiconductor light emitting device can prevent emitted light frombeing reflected or absorbed by electrodes and ensure the maximum lightemitting area by forming the electrodes of semiconductor layers, locatedin a light emitting direction, below an active layer except for part ofthe electrodes, thereby maximizing luminous efficiency.

Further, at least one contact hole is formed in the electrode tosmoothly perform current spreading, such that uniform current spreadingcan be performed with the electrode having a small area.

Further, since the via hole is formed at the upper surface of thesemiconductor light emitting device, alignment is not required duringdie bonding, and wire bonding can be easily performed. In addition,since the semiconductor light emitting device has a vertical structure,wire bonding and die bonding that can be easily performed at low costcan be used together when manufacturing a package. Therefore, massproduction can be achieved at low cost.

Therefore, according to the embodiments of the invention, massproduction of light emitting devices at low cost with high reliabilityand high quality can be realized.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

1. A semiconductor light emitting device having comprising: asemiconductor stack having first and second main surfaces opposing eachother, and comprising first and second conductivity type semiconductorlayers respectively defining the first and second main surfaces, and anactive layer formed between the first and second conductivity typesemiconductor layers; a plurality of conductive vias penetrating thesecond conductivity type semiconductor layer and the active layer, andone region of the first conductivity type semiconductor layer; a firstelectrode layer disposed on the second main surface of the semiconductorstack, the first electrode layer extending and being connected to theone region of the first conductivity type semiconductor layer throughthe conductive vias; and a second electrode layer disposed between thesemiconductor stack and the first electrode layer and connected to thesecond conductivity type semiconductor layer.
 2. The semiconductor lightemitting device of claim 1, further comprising an insulator disposedbetween the first electrode layer and second electrode layer.
 3. Thesemiconductor light emitting device of claim 1, wherein the conductivevias penetrate the second electrode layer to thereby be connected to thefirst electrode layer.
 4. The semiconductor light emitting device ofclaim 1, wherein the second electrode layer comprises a surfaceinterfacing with the second conductivity type semiconductor layer,wherein a portion of the surface is exposed.
 5. The semiconductor lightemitting device of claim 4, further comprising an electrode pad unitdisposed on the exposed portion of the surface of the second electrodelayer.
 6. The semiconductor light emitting device of claim 4, whereinthe exposed portion of the surface of the second electrode layer is aregion exposed by a via hole penetrating the first conductivity typesemiconductor layer, the active layer, and the second conductivity typesemiconductor layer.
 7. The semiconductor light emitting device of claim6, wherein the diameter of the via hole increases in a direction fromthe second electrode layer toward the first conductivity typesemiconductor layer.
 8. The semiconductor light emitting device of claim4, wherein the exposed portion of the surface of the second electrodelayer is formed at an edge of the semiconductor light emitting device.9. The semiconductor light emitting device of claim 1, wherein thesecond electrode layer reflects light generated from the active layer.10. The semiconductor light emitting device of claim 1, wherein thesecond electrode layer comprises one metal selected from a groupconsisting of Ag, Al, and Pt.
 11. The semiconductor light emittingdevice of claim 1, wherein an irregular pattern is formed on a surfaceof the first conductivity type semiconductor layer opposite to anothersurface of the first conductivity type semiconductor layer interfacingwith the active layer.
 12. The semiconductor light emitting device ofclaim 1, further comprises a conductive substrate disposed on the firstelectrode layer and connected to the first electrode layer.
 13. Thesemiconductor light emitting device of claim 12, wherein the conductivesubstrate comprises one metal selected from a group consisting of Au,Ni, Cu, and W.
 14. The semiconductor light emitting device of claim 12,wherein the conductive substrate comprises one selected from a groupconsisting of Si, Ge, and GaAs.